Fabrication of plastic articles by blow-molding is used for one-time use or disposable packaging material. The complete fabrication procedure is carried out in different, consecutive, continuous steps. In this known procedure, the formation of the blank on the blow pipe and the blowing of the blank itself takes only a relatively short time, but the cooling of the blown-up body within the mold takes considerably longer and absorbs the larger part of the cycle time during the fabrication of the hollow body. The time relationship, within certain limits, depends on the material used, on the shape of the hollow body, and on its wall thickness. With this type of operation procedure, a relatively long cycle time exists before the blow pipe is again free for the next molding operation, because the blow pipe is used without interruption during the entire fabrication procedure.
During the blow-molding of bottles with an inside protective layer of a different material than that of the rest of the bottle, it is well known to place the protection layer on the blow pipe first inside a so-called "conditioning chamber" in the shape of a pre-cast form which the hollow body is later formed. Thereafter, the blow pipe with the protection layer or pre-cast is brought into an injection molding device, in which the plastic material is placed around the blow pipe, is positioned underneath the mold station, the two halves of the blow mold being arranged concentrically of the conditioning chamber. After the injection procedure, the conditioning chamber and the blow pipe with the two-layer product is displaced upwardly in the axial direction until it is positioned at the same height as the blow mold which has been previously concentric to the conditioning chamber. Thereafter, the blow mold is closed for the blowing operation. With this arrangement and with these operating conditions, the conditioning chamber, the blowing device, the mold, and the injection device are arranged axially in a vertical line. When the hollow body has been blown up, the blow pipe is removed from the blow mold and inserted into the conditioning chamber, where the protection layer is placed onto the blow pipe for the next hollow body. The pressure inside the hollow body is maintained by compressed air which is introduced through a hole at the side into the closed unit formed by the housing and the extrusion injection device. In order not to influence the application of the protection layer to the blow pipe, the conditioning chamber is closed from the compressed air underneath by dampers.
Such an apparatus, however, is only usable for the fabrication of hollow bodies made from two different materials and can do nothing to reduce the cycle time of the fabrication procedure and to increase the molding procedure per blow pipe and time unit. These and other difficulties experienced with the prior art devices have been obviated in a novel manner by the present invention.
It is, therefore, an outstanding object of this invention to supply the blow pipe with more blank casts in a given time than it is possible with the known procedure.
With this and other objects in view, as will be apparent to those skilled in the art, the invention resides in the combination of parts set forth in the specification and covered by the claims appended thereto.